Table 1.

Summary of typical intermittent fasting/time-restricted eating regimens.

Regimen	Description
Intermittent fasting/time-restricted eating	Most commonly involves fasting for 16–18 hours with an eating window of 6–8 hours, leveraging the natural circadian rhythm. Plain water and unsweetened fluids (black plain tea/coffee) are allowed
Time-restricted feeding	Restriction of caloric intake to specific time periods of the day, typically 8–12 hours during daytime hours. Term typically used in animal studies
Alternate day complete fasting	No calorie intake on fasting days, followed by a day of ad lib intake (eating to satiety)
Alternate day modified fasting	Restricted calorie intake on “fasting” days (<25% daily energy requirements), alternated with days of ad lib intake (eating to satiety)
Periodic fasting	1-2 fasting days/week and 5-6 days of normal caloric intake
5 : 2
6 : 1
Ramadan fasting	Fasting from dawn until sunset followed by ad lib calorie intake after sunset to before dawn. Similar to time-restricted eating but conflicts with circadian rhythm
	No water or fluids during fasting